Military aircraft, in particular helicopters, frequently fly at extremely low altitudes in order to evade enemy attack. Military helicopters may fly at speeds of over 100 knots, and typically fly for extended periods at speeds of 80 knots. Aircraft flying at low altitudes requires a pilot to judge a contour of the ground's surface or the surface of other objects in order to avoid collisions. The pilot's judgment is usually aided by stereoscopic vision and apparent sizes of surface features. However, featureless terrain, such as desert or water, fails to provide features required to judge a contour of the surface. Intensified night vision goggles, used for flying at night, further diminish stereoscopic vision at distances shorter than 50 ft.
As a result, helicopters often contact the desert soil at high speed. In some cases, the contact is significant enough to crash the aircraft, resulting in loss of human life and equipment. This loss can be particularly tragic in times of conflict, when an entire troop may be relying on air support from the helicopter and its pilot.
Some prior art systems have been developed for judging distances, typically for landing purposes. While these systems provide some distance information to the pilot, they do not provide the pilot with a feel for the contour of the surface. Further, reliance on a display can be very distracting to a pilot who must repeatedly shift his focus from the terrain to the display panel.
Therefore, a need has arisen for an apparatus and method to indicate a contour of a surface relative to a vehicle.